A U.S. Marine Corps aircraft carrying four occupants crashed in northern Norway during a NATO exercise Friday evening, according to officials.

None of the occupants survived, Norway's Prime Minister Jonas Gahr Store confirmed Saturday.

"The soldiers participated in the NATO exercise Cold Response," Store said in a statement. "Our deepest sympathies go to the soldiers’ families, relatives and fellow soldiers in their unit."

The exercises in Norway were part of those held annually and were unrelated to the war in Ukraine, The Associated Press reported.

The cause of the crash remained under investigation, the report said.

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The Marines earlier had said only that an "incident" occurred in northern Norway, and that the aircraft was a V-22B Osprey that was part of NATO Exercise Cold Response 22. 

The aircraft belonged to the U.S. military, Norway's armed forces told the AP.

The incident remained under investigation, the Marines said in a Twitter message.

A Bell Boeing V22 Osprey tilt-rotor aircraft with the US Marines, takes off from Naval Air Facility Atsugi in Yamato, Kanagawa, Japan.  (Getty Images)

In a statement provided to Fox News, a spokesperson for the II Marine Expeditionary Force said it was aware of what it described as a "mishap" involving an aircraft in Norway.

The Osprey was on its way to Bodo, where it was scheduled to land about 6 p.m. Friday, but it crashed in Gratadalen in Beiarn, located south of Bodo, the AP reported.

‘Grateful for their efforts’

Norwegian authorities launched a search and rescue effort, the spokesperson added.

"We are grateful for their efforts and will assist them in the search and rescue in all manners possible," the spokesperson said.

Police arriving at the crash site about 1:30 a.m. Saturday confirmed that the crew of four had died, according to the AP.

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Earlier, rescue crews were reportedly headed to the site despite weather conditions in the area that were "challenging" and expected to get worse, Norwegian officials wrote online.

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The Norwegian Armed Forces said the aircraft's last known position was at Saltfjellet, several hundred miles from the Russian border, with parts of Sweden and Finland in the intervening space.

A rescue helicopter was dispatched, but the mission was canceled.

The Associated Press contributed to this story.